A TOC measuring device measures the amount of organic carbon of sample water by subjecting organic carbon contained in the sample water to oxidative decomposition to convert the organic carbon to carbon dioxide, and thereafter measuring the carbon dioxide concentration. Inorganic carbon is contained in sample water prior to subjecting the organic carbon to oxidative decomposition, and total carbon (TC) can be measured by converting the total carbon to carbon dioxide in that state and measuring the carbon dioxide concentration. TOC can also be determined as (TC−IC) by individually measuring TC and IC. On the other hand, when it is attempted to directly measure TOC, a measurement value of organic carbon in a case where IC has not been removed will be greater than the actual value. Therefore, a TOC measuring device is provided with an inorganic carbon removal unit to remove pre-existing inorganic carbon from sample water.
A common treatment that is performed in an inorganic carbon removal unit is an aeration treatment that supplies an aeration gas (sparge gas) to sample water (for example, see Patent Literature 1). To supply an aeration gas to this kind of inorganic carbon removal unit, conventionally, a high purity air cylinder in which the concentration of carbon dioxide and TOC is extremely low is connected to the device, or an air purifier is installed that purifies air by removing carbon dioxide and TOC from the air by combusting the air at a temperature between 700 and 900° C. to convert TOC in the air to carbon dioxide and passing the air through soda lime to cause the soda lime to absorb the carbon dioxide or the like.